Conventional motor vehicles may include an adaptive steering system that may add and subtract an angle between the driver steering wheel input and the steering gear input shaft. An adaptive system may provide enhanced performance at low speeds, such as during parking, and enhanced directional stability at high speeds, such as by using a variable gear ratio. An adaptive steering system may include a locking unit to lock the front steering system of the motor vehicle. The locking unit may provide a mechanical connection between the steering wheel and wheels during power-off of the steering system (i.e., before and/or after shutting down the engine) and may provide a means to lock the steering in case of a failure in the steering system.
Adaptive steering systems have already contributed to significant improvements in controlling an angle input by a driver to a steering wheel and an angle output by the steering gear input shaft, while providing a degree of safety with the locking unit of the steering system. However, adaptive steering systems tend to produce noise when the locking unit is engaged, such as when a motor vehicle is shut down. Such noise may be objectionable to a user but challenging to manage due to the nature of the locking unit and its close proximity to a driver. A past solution to this issue used soft materials to cushion the locking unit and dampen sound created by the locking unit. Another solution uses noises created by events, such as the engine shutting off or other sounds created by the vehicle, to mask the noise created by the locking unit but this increased the overall noise of the vehicle at shut down. Other solutions included maintaining full power to the adaptive steering system and after engine shut off so the locking unit remains unlocked, but this would require high power consumption from the vehicle battery, such as when a driver applied a torque to the steering wheel (e.g., as an aid to exit the vehicle) while the engine was shut off.
In view of these considerations, further improvements may be made to steering systems for motor vehicles so a noise made by locking units of the steering systems is less objectionable for a user of a motor vehicle.